This invention pertains to a process for the preparation of 3-buten-1-ol from 3,4-epoxy-1-butene (EPB). More specifically, this invention pertains to the synthesis of 3-buten-1-ol by contacting EPB and formic acid with a catalyst solution comprising a palladium(0) compound, a tertiary phosphine and a tertiary amine.
3-Buten-1-ol is an important intermediate in the production of pharmaceuticals. The palladium-catalyzed coupling of 3-buten-1-ol with aryl halides is a valuable process for the preparation of aryl-substituted aldehydes (R. C. Larock et al., Tetrahedron Letters, 30, 6629 (1989)). This coupling process is used in the production of antifoliate compound Pemetrexed disodium (U.S. Pat. No. 6,262,262).
U.S. Pat. No. 3,574,773 discloses the preparation of 3-buten-1-ol by reacting propylene with aqueous formaldehyde in the presence of a base such as ammonia at a temperature of 235 to 400xc2x0 C. and a pressure of 50 to 500 atmospheres. U.S. Pat. Nos. 4,261,901 and 4,288,374 also describe the preparation of 3-buten-1-ol by reacting propylene and aqueous formaldehyde stabilized with an alcohol in the presence of silica sand at a temperature of 250 to 350xc2x0 C. and a pressure of 50 to 800 atmospheres. A 27% conversion of formaldehyde to 3-buten-1-ol is reported in an example.
U.S. Pat. No. 5,406,007 discloses a process for preparing a mixture of 2-buten-1-ol (crotyl alcohol) and 3-buten-1-ol by the hydrogenation of EPB in the presence of a sulfur-modified or sulfided nickel catalyst.
J. Tsuji et al., Chem. Letters, 1017 (1984) disclose the homogeneous transfer hydrogenation of EPB to 3-buten-1-ol by heating a mixture of EPB, tris(dibenzylideneacetone)dipalladium(0)-chloroform adduct, tri-n-butylphosphine, ammonium formate and dioxane solvent at 100xc2x0 C. for one hour. Ammonium formate is the source of hydrogen in this process and carbon dioxide is a by-product. The use of the Tsuji et al. process to manufacture 3-buten-1-ol on a commercial scale is not practical because of the toxicity of dioxane and chloroform (suspected carcinogens) and the production of a white solid during the operation of the process. This white solid is believed to be a mixture of ammonium formate and ammonium carbonate formed from ammonia and carbon dioxide derived from the ammonium formate. The white solid can foul and plug process equipment such as condensers which may lead to hazardous build up of pressure within the equipment and reactor.
U.S. Pat. No. 6,103,943 discloses a batch process for preparing 3-buten-1-ol from EPB on a commercial scale. In this process, EPB is converted to 3-buten-1-ol by contacting EPB and formic acid with a catalyst solution comprising a palladium(0) compound, a tertiary phosphine, and a trialkylamine in tetrahydrofuran (THF). At the conclusion of the process, the catalyst is normally deactivated by the addition of 30% hydrogen peroxide and/or cupric chloride. The deactivation of catalyst is said to be needed to prevent isomerization of product to 2-buten-1-ol during distillation of the product from the reaction mixture. This process has several serious drawbacks which result in inefficient and expensive production of 3-buten-1-ol. The single batch use of the expensive palladium(0) catalyst results in less than 6000 moles of 3-buten-1-ol per gram-atom palladium (catalyst turnovers). THF is an expensive solvent which must be removed by efficient fractional distillation. Deactivation of the palladium catalyst with cupric chloride results in a copper mirror on the inside surface of the reaction vessel which must be removed prior to the next batch. Removal of this mirror is a costly and hazardous process requiring the use of hot, aqueous nitric acid.
An improved process has now been discovered which permits, in addition to a batch mode of production, the continuous or semi-continuous production of 3-buten-1-ol from EPB. In batch, continuous or semi-continuous processes, EPB is converted to 3-buten-1-ol by addition of EPB and formic acid (reactants) to a catalyst solution comprising a palladium(0) compound, a tertiary phosphine, a tertiary amine and an organic reaction solvent. The continuous or semi-continuous process for the preparation of 3-buten-1-ol provided by the present invention comprises the steps of:
(1) feeding EPB and formic acid to a reaction zone containing a catalyst solution comprising a palladium(0) compound, a tertiary phosphine, a tertiary amine and an organic solvent, to form a reaction mixture, maintained at an elevated reaction temperature; and
(2) distilling the contents of the reaction zone to remove a vapor comprising 3-buten-1-ol;
wherein the organic solvent comprises 3-buten-1-ol, an extraneous solvent having a boiling point of at least 130xc2x0 C., or a mixture thereof.
As is discussed in further detail below, the foregoing process steps may be performed sequentially or in a substantially simultaneous manner. The continuous or semi-continuous process of the present invention allows the extended use of the expensive palladium(0) catalyst, and allows the product to be distilled from the reaction mixture with little or no product isomerization. Thus, in accordance with the present invention the catalyst may be used over extended periods of time to achieve greater than 30,000 catalyst turnovers resulting in improved efficiency and lower cost operation.